/*
  将下面异步代码使用 Promise 的方法改进
  尽量用看上去像同步代码的方式
  setTimeout(function () {
    var a = 'hello'
    setTimeout(function () {
      var b = 'lagou'
      setTimeout(function () {
        var c = 'I ♥ U'
        console.log(a + b +c)
      }, 10)
    }, 10)
  }, 10)
*/

//  解决回调，即解决setTimeout的调用顺序问题
new Promise((resolve) => {
    setTimeout(() => {
        resolve('hello');
    }, 10);
}).then(value => {
    return new Promise(resolve => {
        setTimeout(() => {
            resolve(value + 'lagou');
        }, 10);
    });
}).then(value => {
    return new Promise(resolve => {
        setTimeout(() => {
            resolve(value + 'I ♥ U');
        }, 10);
    });
}).then(value => {
    console.log(value);
});

